1. Field of the Invention
The present invention relates to an annealed single-crystal CVD diamond having an extremely high toughness. The invention also relates to a process for producing a single-crystal CVD diamond in three dimensions on a single crystal diamond substrate using Microwave Plasma Chemical Vapor Deposition (MPCVD) within a deposition chamber.
2. Description of Related Art
Large-scale production of synthetic diamond has long been an objective of both research and industry. Diamond, in addition to its gem properties, is the hardest known material, has the highest known thermal conductivity, and is transparent to a wide variety of electromagnetic radiation. Monocrystalline diamond in particular possess a wide range of important properties, including a low coefficient of thermal expansion, the highest known thermal conductivity, chemical inertness, wear resistance, low friction, and optical transparency from the ultra-violet (UV) to the far infrared (IR). Therefore, it is valuable because of its wide range of applications in a number of industries and research applications, in addition to its value as a gemstone.
For at least the last twenty years, a process of producing small quantities of diamond by chemical vapor deposition (CVD) has been available. As reported by B. V. Spitsyn et al. in “Vapor Growth of Diamond on Diamond and Other Surfaces,” Journal of Crystal Growth, vol. 52, pp. 219-226, the process involves CVD of diamond on a substrate by using a combination of methane, or another simple hydrocarbon gas, and hydrogen gas at reduced pressures and temperatures of 800-1200° C. The inclusion of hydrogen gas prevents the formation of graphite as the diamond nucleates and grows. Growth rates of up to 1 μm/hour have been reported with this technique.
Subsequent work, for example, that of Kamo et al. as reported in “Diamond Synthesis from Gas Phase in Microwave Plasma,” Journal of Crystal Growth, vol. 62, pp. 642-644, demonstrated the use of Microwave Plasma Chemical Vapor Deposition (MPCVD) to produce diamond at pressures of 1-8 kPa at temperatures of 800-1000° C. with microwave power of 300-700 W at a frequency of 2.45 GHz. A concentration of 1-3% methane gas was used in the process of Kamo et al. Maximum growth rates of 3 μm/hour have been reported using this MPCVD process. In the above-described processes, and in a number of other reported processes, the growth rates are limited to only a few micrometers per hour.
Methods of improving the growth rates of single-crystal chemical vapor deposition (SC-CVD) diamonds have recently been reported, and these methods have opened new opportunities for the application of diamond for gems, optics, and electronics.
U.S. Pat. No. 6,858,078 to Hemley et al. is directed to an apparatus and method for diamond production. The disclosed apparatus and method can lead to the production of diamonds that are light brown to colorless.
U.S. patent application Ser. No. 10/889,171 is directed to annealing single-crystal chemical vapor deposition diamonds. Important inventive features include raising the CVD diamond to a set temperature of at least 1500° C. and a pressure of at least 4.0 GPa outside of the diamond stable phase.
U.S. patent application Ser. No. 10/889,170 is directed to diamonds with improved hardness. The application discloses a single-crystal diamond with a hardness greater than 120 GPa.
U.S. patent application Ser. No. 10/889,169 is directed to diamonds with improved toughness. The application discloses a single-crystal diamond with a fracture toughness of 11-20 MPam1/2 and a hardness of 50-90 GPa.
The aforementioned disclosures do not disclose single-crystal diamonds having a toughness over 20 MPam1/2. Nor do they disclose methods to produce single-crystal diamond with growth in three dimensions on a single crystal diamond substrate.